We investigate the transport properties of oue dimensional silicon-carbon ［（SiC）n］ and alumium- nitrogen ［（Al-N）n］ nano-wires coupled to two Al（100） electrodes based on a recently developed ab-initio nonequilibrium Green function formalism.The equilibrium conductance of silicon-carbon and alumium-nitrogen nano-wires decrease with the length of wires. The charge transfer of silicon-carbon increases monotonically with the the length of wires. On the contrary, the charge transfer of alumium-nitrogen nano-wire decreases monotonically with the increasing length of wires. The charge transfer changes almost linearly with increasing gate-voltage for both nano-wires and the variation of the equilibrium conductance is different for the wires. With the increase of the gate-voltage, both nano-wires might be good candidates for molecular switch, especially the （AlN）5 nano-wires.